The Effect of Acute Pulmonary Hypertension on Tricuspid Annular Height, Strain, and Curvature in Sheep.

The tricuspid annulus shows significant alterations in patients with functional tricuspid regurgitation-tricuspid valve dysfunction that is secondary to other diseases such as pulmonary hypertension. Early changes in annular shape and dynamics may provide an understanding of disease mechanisms and could predict disease progression. To gain a mechanistic insight into these early changes we perform a spatially-resolved analysis of the effect of acute pulmonary hypertension on the tricuspid annulus in sheep. To this end, we suture sonomicrometry crystals to the annulus of nine sheep and record their locations in the beating heart, before and after inducing acute pulmonary hypertension. Using least-squares cubic splines, we derive mathematical representations of the annulus to describe pulmonary hypertension-induced annular shape changes via strain, relative curvature, and relative annular height between the control group and the acute pulmonary hypertension group. Moreover, we determine hypertension-induced alterations to annular dynamics as within-group strains, relative curvature, and relative height throughout the cardiac cycle for each group. We confirm that the annulus in acute pulmonary hypertension dilates significantly, becomes more circular, and flattens. Our regional analysis reveals that annular dilation, circularization, and flattening are driven by highly localized changes in annular strains, curvature, and height. Additionally, we find that acute pulmonary hypertension alters annular dynamics, albeit minimally. This regionally-resolved analysis of acute hypertension-induced changes of annular shape and dynamics provides insight into early disease mechanisms, and may inspire future generations of annuloplasty devices and techniques that address spatial annular heterogeneities.